The invention relates to an air cycle machine to be used in a transport machinery, such as an aircraft, shipping and vehicle, and an air conditioning system using the same, especially, an air conditioning system for an aircraft for supplying pressurized air into a cabin of the aircraft, and ventilating the same accompanied by heating and cooling.
For example, an aircraft generally includes an air conditioning system for supplying conditioned air with optimum temperature and pressure to a pressurized cabin or chamber, such as an accommodation compartment and an electronics"" chamber. The air conditioning system plays various roles, such as dehumidifying, supplying oxygen to the pressurized cabin and making up for leaked air, in addition to regulating temperature and pressure of air. To play these roles, it is indispensable to take open or outside air.
In case the open air is taken as described above, if air cooling is made only by ram air, it can not respond immediately. Also, it is impossible to obtain a sufficient pressure necessary for the pressurization from thin ram air during a high altitude flight. If the open air is taken as it is, pressure and oxygen quantities necessary for the pressurized cabin can not be obtained. Therefore, there has been established an air conditioning system, wherein bleed air is obtained from an engine (including an auxiliary power portion) where a sufficient quantity of the open air always exists, and the temperature and pressure of the engine bleed air are regulated to supply to the pressurized cabin as air conditioned or regulated air.
An air cycle machine ACM of the air conditioning system as a main part thereof is generally structured such that, as shown in FIG. 1, a turbine T is driven by engine bleed air BA of an engine 20, the turbine power is transmitted to a compressor C connected by a single shaft, and the engine bleed air BA to be supplied to the turbine T is compressed by the compressor C and supplied to a pressurized cabin 22. In FIG. 1, reference numeral 21 represents a bootstrap circuit for supplying the engine bleed air BA discharged from the compressor C to the turbine T, and PHX and SHX represent heat exchangers.
In the structure as described above, since a work more than the turbine power can not be done by the compressor, it is indispensable to balance a work quantity of the compressor and the turbine power.
However, in case the driving power of the turbine relies on only the engine bleed air, a performance of the air cycle machine is inevitably governed by the bleed air pressure and flow quantity. For example, when the bleed air flow quantity is small, the turbine power is reduced to thereby lower the performance of the air cycle machine, which results in lowering a cooling performance of the whole air conditioning system. Therefore, with the structure of the conventional air cycle machine, there is a problem such that an effective flight and a suitable air conditioning are incompatible.
Also, in a passenger airplane where a large number of passengers are on board, a large quantity of ventilation air is required. Thus, in case the whole necessary quantity of ventilation air is taken from the engine bleed air, the quantity of the engine bleed air is increased and an engine penalty (fuel consumption) is increased to thereby greatly reduce an efficiency of the aircraft.
In order to solve the above problems, the present invention has been made, and an object of the invention is to provide an air cycle machine and an air conditioning system using the same, wherein air conditioning can be effectively made by using bleed air and open air.
According to a first aspect of the invention, in an air cycle machine, a turbine is driven by an engine bleed air, and a turbine power is mechanically transmitted to a compressor. The engine bleed air to be sent to the turbine is compressed by the compressor, and if necessary, the compressor is electrically driven to thereby structure a hybrid-type air cycle machine.
When the air cycle machine is structured as described above, even if the turbine power is decreased pursuant to the decrease in the flow rate and pressure of the engine bleed air, the turbine can also be electrically driven to provide a predetermined turbine power and raise a compression ratio of the compressor, so that an expansion ratio of the turbine is increased. Therefore, a temperature at the exit of the turbine is lowered to thereby prevent the cooling ability from being lowered.
According to a second aspect of the invention, there is provided an air conditioning system using the hybrid-type air cycle machine, wherein the engine bleed air is introduced into the compressor to be compressed therein, is cooled in the heat exchanger, and then is subjected to an adiabatic expansion in the turbine to self-cool to thereby obtain conditioned air without requiring a high-pressure bleed air source, what is called, to structure a bootstrap circuit.
According to a third aspect of the invention, there is provided another air conditioning system using the hybrid-type air cycle machine as described above, wherein the engine bleed air is introduced into the turbine to drive the same, while the open air is taken to be compressed at the compressor to thereby structure a circuit for obtaining conditioned air from the compressed open air and the bleed air expanded at the turbine.
Of course, the inventions according to the second and third aspects may be included in one air conditioning system.
According to a fourth aspect of the invention, in an air conditioning system for an aircraft formed of an air cycle machine, as an essential portion thereof, wherein a turbine and a compressor is connected by a single shaft, engine bleed air is introduced into the turbine to drive the air cycle machine, while the open air is introduced into the compressor to raise its pressure for a ventilation air.
According to this structure, since the open air is compressed by the turbine due to the engine bleed air and can be used as ventilation air, the usage of the engine bleed air can be reduced to thereby suppress the fuel penalty or consumption of the engine.
Incidentally, the open air is normally taken through a ram duct, but it may be taken by air-bleeding from a fan bleed.